1. Field of the Invention
The present invention relates to a current location displaying apparatus in which a path of travel of a running body, such as an automobile, is displayed on a display screen which has a map perviously displayed thereon.
2. Description of the Prior Art
Recently, in an attempt to provide guidance to a driver of an automobile to prevent the driver from losing his way, during driving, for example, in a strange place, there has been developed a current location displaying apparatus, as hereinafter described more in detail, in which a running distance and a running direction of the running body are detected, from time to time, and a current location of the running body on two-dimensional coordinates is successively computed from results of such detections, whereby the current location of the running body is successively displayed on a map which is previously displayed on a screen.
In such current location displaying apparatus, it is difficult to avoid occurrence of a positional error owing to precision of detections at the time of detecting the distance and the direction during running of the running body, and such positional error is progressively integrated, as the running body continues its running, with the result that the current location comes off the running course on the map until the driver becomes unable to see where he is driving.
One pratice to correct such positional error by effecting matching between a pattern of a road on a map and a pattern of current location of the running body which is obtained by storing and holding data of the successively changing current location as the running body continues its running, thereby enabling correction of the current location which has come off the running course. According to this method, a plurality of roads which are considered to be the roads through which the running body has passed are selected from a complicated road network in any manner, and adaptability of the pattern of each of the extracted roads and the pattern of the current location of the moving body is examined. Then, the road having highest matching rate is assumed as a road where the running body is actually running and the correction in position is effected as the current location of the moving body comes onto the road to which the matching has been effected.
In such method, if the map includes complicated roads, considerable number of road patterns are extracted as the roads which are considered to be the ones through which the moving body has passed.
It is, therefore, necessary to effect matching of the pattern of the travel path to each of the road patterns, so that the processing is very complicated and requires considerable time. This method has a further disadvantage in that if the running body passes through a road which does not exist on the map, the pattern matching cannot be effected, with the result that the correction of the current location becomes impossible.